Circuit breaker contact pressure adjusting means



Feb. 15, 1966 J. c. BRUMFIELD CIRCUIT BREAKER CONTACT PRESSURE ADJUSTINGMEANS 3 Sheets-Shea?l 1 Filed Dec. 11, 1963 A 4/ 4/ //vf -NIE Feb. 15,1966 J. c. BRUMFIELD 3,235,699

CIRCUIT BREAKER CONTACT PRESSURE ADJUSTING MEANS Filed Dec. ll, 1963 5Sheets-Sheet 2 l-I E115- Feb. 15, 1966 J. c. BRUMFIELD CIRCUIT BREAKERCONTACT PRESSURE ADJUSTING MEANS Filed DSC. ll, 1963 5 Sheets-Sheet 5INVENTOR, Ja//A/ C www-na United States Patent O 3,235,699 CIRCUITBREAKER CGNTACT PRESSURE ADJUSTING MEANS John C. Brumiield,Philadelphia, Pa., 'assigner to I-T-E Circuit Breaker Company,Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 11, 1963,Ser. No. 329,689 9 Claims. (Cl. 200-170) This invention relates to meansfor adjusting circuit breaker contact pressure without disturbing thespacing between the contacts in the open position thereof. Moreparticularly, this invention is an improvement over the contact pressureadjusting means disclosed in the copending application U.S. Serial No.174, 767 tiled February 21, 1962, entitled Means for Adjusting ContactPressure, with I. C Brumtield et al. `as inventors and .assigned to theassignee of the instant invention.

In circuit breakers having quick make and quick break features themovable contact moves at a very high rate of speed into engagement withthe stationary contact upon closing of the circuit breaker. Thus, it isnecessary to provide means for absorbing the energy released by theclosing mechanism in a very short travel of the movable contact.

In the circuit breaker art this has traditionally been accomplished bymounting the stationary Contact on a spring or providing a spring whichis interposed between the movable Contact and the closing mechanism.Such springs must be of considerable strength to maintain high pressurebetween the contacts when they are in engagement so that good electricalcontact is maintained in spite of magnetic blow-oil:` forces whichaccompany current flow. Because of manufacturing tolerances it isnecessary to adjust the contact pressure after the Contact operatingmechanism and stationary contacts are mounted to the circuit breakerbase.

In recent years circuit breaker constructions have become so compactthat nding room for adjusting the movable contact in the open positionof the circuit breaker has presented a problem. That is, in order toachieve etlicient circuit interruption and prevent restriking of an arc,there is a minimum distance required for contact separation in the openposition of the circuit breaker.

Prior to the invention described in the aforesaid copending application,Serial No. 174,767, prior art means for adjusting contact pressure waslimited for the most part to the tedious process of shimming up thestationary contact and the lengthening or shortening of the Contactpressure springs. The invention set forth in the aforesaid copendingappli-cation Serial No. 174,767 has proven entirely satisfactory fromthe adjusting and operating viewpoints whereas the other prior artmethods have proved unsatisfactory since adjustments of contact pressureresulted in the changing of the gap between the contacts in the openposition of the circuit breaker.

The instant invention retains the advantages of the invention set forthin aforementioned copending application Serial No. 174,767 without anyof the disadvantages of prior art construction. In addition, the instantinvention sets forth a construction which is more compact than that ofthe prior art and is especially economical to produce.

More particularly, the device of the instant invention provides anadjusting nut threada'bly mounted to a short screw. Contact springpressure and the fact that the screw head is captured in a recess of thecontact carrier mounts the screw to the carrier. The contact pressurespring bears against the movable contact arm and the adjusting nuturging the arm away from the nut. The adjusting nut is provided with aplurality of circularly arranged axially extending tabs which form anopen ended cage to conline the end of the spring seated against the nutagainst transverse movement.

By rotating the nut relative to the screw, spring pressure is adjustedas required. After the nut is rotated to position such that the requiredcontact pressure is obtained, the nut is maintained in this position bybending two of the circularly arranged tabs outwardly to radialpositions. The radially extending tabs are so positioned that one or theother thereof will engage the contact carrier should the adjusting nutattempt to rotate and in this way rotation of the adjusting nut isprevented.

Accordingly, a primary object of this invention is to provide a circuitbreaker having novel means for adjusting pressure between cooperatingcontacts.

Another object is to provide novel contact pressure adjusting meanswhich, during the adjusting process, will not affect the gap settingbetween contacts in the open position of the circuit breaker.

Still another object is to provide a contact pressure adjusting nuthaving a plurality -of bendable tabs movable to positions forcooperating with the contact carrier to prevent rotation of theadjusting nut after the desired contact pressure is obtained.

These as well as other objects of the instant invention shall becomereadily apparent after reading the following description of theaccompanying drawings, in which:

FIGURE 1 is a longitudinal cross-section taken through the center phaseof a multi-phase molded case -circuit breaker constructed in accordancewith the teachings of the instant invention.

FIGURE 2 is a side elevation of the Contact operating mechanism withcertain elements removed to better reveal the structure of otherelements.

FIGURE 3 is a plan View showing the contact carrier and elements mounteddirectly thereto when disconnected from the operating mechanism.

FIGURE 4 is a cross-section `taken through line 4-4 of FIGURE 3 lookingin the direction of arrow 4-4.

FIGURE 5 is a `front elevat-ion of the elements of FIG- URE 3 looking inthe direction of arrows 5-5 of FIG- URE 4.

FIGURE 6 is an exploded perspective illustrating the construction of thecontact pressure adjusting means.

Now referring to the gures. Circuit breaker 10` includes a moldedhousing comprising base 11 and Iremovable cover 12 joined together alongline 13. Suitable barriers in base 11 and cover 12 divide the housinginto three longitudinally extending compartments, each housing `theelements of an individual phase of circuit breaker 10. Since the currentcarrying ele-ments of all three phases are substantially identical, forthe sake `of brevity, only the current carrying elements of the centerphase will be described. 'Ihe current path between line termin-a1 15 andload terminal strip 16 proceeds from stationary contacts 17 and 24 online terminal strip 15, to movable contacts 18 and 25 carried by contactarms 19 and 26, through tr-ifurcated laminated dexible conductor 2li andclamp 21 to bimetal heater 22, and then to load terminal str-ip 16.

Since circuit breaker is of relatively high current,

carrying capacity, contacts 17, 1S function as arcing contacts which areparalleled by .two sets of main contacts, each comprising a stationaryycontact 24 and a cooperating movable contact 25. Movable contacts 25are each mounted to individual contact arms 26 with each of the arms 26being connected by an individual section of conductor to clamp 21 whilestationary contacts 24 are mounted to line terminal strip 15.

Circuit breaker 1G also includes an automatic tripping mechanism 28 anda toggle operating mechanism 29, each Well known to the art. The detailsof mechanisms 28 and 29 form no part of this invention. For details ofthese mechanisms reference is made to copending application Serial No.108,812 Itiled May 9, 1961, in the name of E. Wortman, now U.S. PatentNo. 3,155,802, entitled U-Shaped Cradle for Circuit Breaker and assignedto the assignee of the instant invention.

Operating mechanism 29 is connected to the contacts of all three phasesby means of transverse insulating tie bar 30. Individual V-shaped straps31 connect all three contact carriers 32 to tie bar 30, so that theContact pairs corresponding to one another in the different phases areoperated into and out of engagement simultaneously.

Contact carrier 32 of the center phase is connected at pin 36 to thelower end of the operating mechanism toggle 34, 35. As is well known tothe art, cooperating main contacts 2'4, 25 separate prior to theseparation of the cooperating arcing contacts 17, 18 when the circuitbreaker 10 is being opened and upon closing of the circuit breaker 1@arcing contacts 17, 18 engage prior to the engagement of main contacts24, 25. Movable contact arm 19 is pi-votally mounted to carrier 3-2 atpin 43. Spring means 44, constituted by a plurali-ty of leaf springsarranged in stack, is anchored at one end to carrier 32 by means ofscrews 45. The other end of spring means 44 engages roller 46 pivotallymounted at the free end of contact arm 19 to bias arm 19 in acounterclockwise direction (with rsepect to FIGURE 2) about pin 43',with this motion being limited through the engagement of the right endof arm 19 with the bottommost of the springs in stack 44.

Each of the contact arms 26 is pivotally mounted to carrier 32 on anindividual pin 43. Contact pressure springs 51, 52 bias contact arm 26in a counterclockwise direction (with respect .to FIGURE 4) about pin43, with this motion being limited in the open circuit position ofcircuit breaker 10 through the engagement of the right end of arm 26with carrier surface 53. Springs 51, 52 are concentrically wound coilunits with spring 52 being mounted within spring 51. The lower end ofsprings 51, 52 abut the upper surface of contact arm 26 at the endthereof to the left of pivot 43. The upper ends of springs 51, 52 abutadjusting nut 55 and are aligned with the central threaded aperture 56of nut S5. The threads of aperture 56 are in engagement with the`threads of screw 57.

Nut 55 is a flat circular member having a plurality of bendable tabspositioned around the periphery thereof. As will become more readilyapparent, prior to making the final adjustment of contact pressure allof the tabs 60 extend in a downward or axial direction so as to form anopen-ended cage which contines the upper end of springs 51, 52 againsttransverse movement. Boss 59, projecting upwardly from contact arm` 26,prevents transverse movement of the lower end of springs 51, 52. Theunderside of the upper wall of carrier 32 is undercut to form a recesswhich houses head 61 of screw 57. A portion of head 61 is deformed toform radial projection 61a which fits into carrier notch 63 therebypreventing rotation of screw 61 relative to carrier 32.

In order to adjust the degree of pressure exerted by springs 51, 52 uponcontact arm 26, nut 55 is rotated while screw 57 remains tixed. Thus,nut 55 moves in an axial direction with respect to springs 51, 52thereby lengthening or shortening springs 51, 52 as desired, and -by sodoing controlling the pressure exerted thereby. When lthe desiredpressure is obtained, `the exposed tabs 60 nearest vertical walls 32a,321; of carrier 32 are bent outwardly so that they extend radiallyoutward. With tabs 66a and 60h extending radially, rotation of nut 55 inone direction is prevented through the engagement of tab 60a with wall32a and rotation of nut 55 in the opposite direction is preventedthrough the engagement of tab 6017 with wall 3217 so that the adjustedpressure setting for springs 51, 52 is maintained.

Thus, this invention provides a means, of especially simplifiedconstruction, for adjusting circuit breaker contact pressure withoutaltering or in any way affecting the open circuit position of thecooperating contacts.

Although this invention has been described with respect to preferredembodiment thereof, it should be understood that many variations andmodifications will now be obvious to those skilled in the art, and it ispreferred therefore that the scope of the invention be limited not bythe specific disclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are deiined as follows:

1. A circuit breaker including a pair of cooperating contacts; an armcarrying one of said contacts; a carrier to which said arm is mounted;an operating mechanism connected to said carrier for moving said armbetween a first and a second position wherein said contacts aredisengaged and engaged respectively; first means for establishing thegap separation between said pair of contacts when in said firstposition; spring means acting between said arm and said carrier to exertpressure between said contacts when said arm is in said second position;and second means for adjusting the degree of pressure exerted lby saidspring means when said arm is in said second position Without alectingthe gap separation established by said tirst means; said second meansincluding a threaded member carried by said carrier and a nut threadablymounted to said member; means maintaining said member against rotation;said nut in operative engagement with said spring means whereby movementof said nut relative to said member results in changing the pressureexerted by said spring means when said arm is in said second position.

2. A circuit breaker as set forth in claim 1 in which the threadedmember is a screw having a bead disposed Within a recess of said carrierdefined by boundary means integrally formed with said carrier.

3. A circuit breaker including a pair of cooperating contacts; an armcarrying one of said contacts; a carrier to which said arm is mounted;an operating mechanism connected to said carrier for moving said armbetween a first and a second position wherein said contacts aredisengaged and engaged respectively; spring means acting between saidarm and said carrier to exert pressure between said contacts when saidarm is in said second position; and means for adjusting the degree ofpressure exerted by said spring means when said arm is in said secondposition; said means including a threaded member carried by said carrierand a nut threadably mounted to said member; means maintaining saidmember against rotation; said nut in operative engagement with saidspring means whereby movement of said nut relative to said memberresults in changing the pressure exerted by said spring means when saidarm is in said second position; said nut is provided with bendable meanspositionable for cooperation with portions of said carrier to preventmovement of said nut relative to said threaded member.

4. A circuit breaker as set forth in claim 3 in which the bendable meansincludes a plurality of tabs arranged along the periphery edge of saidnut,

5. A circuit breaker as set forth in claim 4 in which the spring meansis a coiled member; at least some of said plurality of tabs extendingparallel to the axis of said coiled member and constituting means forconfining one end of said coiled member against transverse movement.

6. A circuit breaker as set forth in claim 5 in which a rst of saidplurality of tabs is radially extending.

7. lA circuit breaker as set forth in claim 6 in which a second of saidplurality of tabs is radially extending.

S. A circuit breaker as set forth in claim 6 in which the threadedmember is a screw having a bead disposed within a recess of said carrierdefined by boundary means integrally formed with said carrier.

9. A circuit breaker as set forth in claim 8 in which References Citedby the Examiner UNITED STATES PATENTS 12/1949 Sandin et al. .ZOO-166 X5/1964 Murphy 20G-170 KATHLEEN H. CLAFF Y, Primary Examiner.

BERNARD A. GILHEANY, Examiner.

1. A CIRCUIT BREAKER INCLUDING A PAIR OF COOPERATING CONTACTS; AN ARM CARRYING ONE OF SAID CONTACTS; A CARRIER TO WHICH SAID ARM IS MOUNTED; AN OPERATING MECHANISM CONNECTED TO SAID CARRIER FOR MOVING SAID ARM BETWEEN A FIRST AND A SECOND POSITION WHEREIN SAID CONTACTS ARE DISENGAGED AND ENGAGED RESPECTIVELY; FIRST MEANS FOR ESTABLISHING THE GAP SEPARATION BETWEEN SAID PAIR OF CONTACTS WHEN IN SAID FIRST POSITION; SPRING MEANS ACTING BETWEEN SAID ARM AND SAID CARRIER TO EXERT PRESSURE BETWEEN SAID CONTACTS WHEN SAID ARM IS IN SAID SECOND POSITIONS; AND SECOND MEANS FOR ADJUSTING THE DEGREE OF PRESSURE EXERTED BY SAID SPRING MEANS WHEN SAID ARM IS IN SAID SECOND POSITION WITHOUT AFFECTING THE GAP SEPARATION ESTABLISHED BY SAID FIRST MEANS; SAID SECOND MEANS INCLUDING A THREADED MEMBER CARRIED BY SAID CARRIER AND A NUT THREADABLY MOUTEED TO SAID MEMBER; MEANS MAINTAINING SAID MEMBER AGAINST ROTATION; SAID NUT IN OPERATIVE ENGAGEMENT WITH SAID SPRING MEANS WHEREBY MOVEMENT OF SAID NUT RELATIVE TO SAID MEMBER RESULTS IN CHANGING THE PRESSURE EXERTED BY SAID SPRING MEANS WHEN SAID ARM IS IN SAID SECOND POSITION. 